The invention claimed and disclosed herein pertains to protection of disk drives in disk array systems, such as a Redundant Array of Independent Disks (xe2x80x9cRAIDxe2x80x9d) storage system, from external and/or internal mechanical disturbances. The present invention especially relates to the use of viscoelastic foam materials to protect arrays of disk drives from such disturbances.
Since RAID storage systems are one of the most important forms of disk drive arrays, they will be used to illustrate and differentiate the present invention. However, it is understood that the present invention pertains to the protection of disk drives in any disk array system. Generally speaking, RAID storage systems are arrays of disk drives (xe2x80x9cDDsxe2x80x9d) controlled by one or more controllers. Higher data transfer rates are achieved through the ability of the system""s controller to schedule, read and write commands to multiple DDs in a parallel fashion. Such storage systems employ one or more motor driven spindles that rotate the DDs at several thousand revolutions per minute. Such systems also have a printed circuit board that receives commands from the controller and translates them into voltage fluctuations that cause a head actuator to move an array of ganged read/write heads across a complimentary array of disks. The head actuator must push and pull each gang with the extreme precision required to properly position a given head with select tracks that lie in concentric circles on the surface of a disk being served by that head. In short, disk drive systems are very precise, and very delicate, pieces of equipment that must be protected from mechanical shocks and vibrationsxe2x80x94from whatever source.
Therefore, owing to their mechanical sensitivities, these systems are shipped to their end users in external packaging systems that include extra and/or specifically designed, and hence expensive, foam padding systems. Those skilled in the disk drive arts also will appreciate that a RAID system""s DDs are especially susceptible to external mechanical disturbances. Consequently, these DDs are shipped separately from the rest of the RAID system. The individual DDs are usually placed in compartmentalized, foam-lined, boxes and static electricity resistance bags. Aside from its greater packaging and shipping costs, this practice also adds a great deal to the setup time when a RAID system is unpacked and installed.
Aside from carefully packing their products for shipping in external foam padding systems, RAID system manufacturers also have provided compliant mounting systems for individual DDs in order to protect them from external mechanical disturbances during use of the RAID system. For example, some manufacturers have followed the practice of placing a compliant medium between each DD and the structure to which the individual DDs are mounted. These DDs are mounted to their support structure in this compliant manner in order to filter potentially harmful external mechanical disturbances. Unfortunately, a RAID""s throughput performance can be diminished as a result of this type of compliant mounting of individual DDs to their DD support structure. That is to say that, under the compliant mounting conditions between the individual DDs and the DD support structure, the DDs can exhibit diminished throughput performance due to certain self-induced vibrations, which the compliant mountings permit to occur. For example, under these compliant mounting conditions, servomechanism movements of individual DDs can cause rotational vibration disturbances that can cause one or more DDs in a DD array to become self-disturbed or self-excited. It is also possible for DDs to be adversely affected by translational forces from external sources after they are placed in operation. These forces can cause a temporary misalignment of the magnetic head used to read and write date from and to the magnetic disk medium in the DD. This temporary misalignment can in turn result in a read/write data error, requiring the data to be re-read from, or rewritten to, the magnetic media, affecting the performance (rate of data transfer) of the RAID system.
What is needed then is a disk array system, which achieves the benefits to be derived from similar prior art devices, but which avoids the shortcomings and detriments individually associated therewith.
One embodiment the invention provides for a disk drive enclosure system having an enclosure and a cage configured to mount a plurality of disk drives. The disk drive enclosure system also includes foam between the cage and the enclosure. The foam, which has characteristics of compliance (i.e., deformation under a load) and damping (i.e. resistance to movement that is proportional to speed), has a plurality of voids selectively formed therein. Preferably, the voids are selectively formed to thereby increase the compliance of the foam over a similar foam which does not have the voids selectively formed therein. That is, the compliance of the foam can be xe2x80x9ctunedxe2x80x9d or adjusted (typically increased) by selectively forming the voids in the foam. The voids can be formed through the entire thickness of the foam so as to form open passageways in the foam. The voids can also be formed through only a portion of the thickness of the foam to basically form pockets in the foam. The foam can be a foam system, which includes a plurality of foam components, in which case the voids can be formed only in selected ones of the foam components. In one variation the foam is fabricated from a plurality of foam pieces having different geometries, and the differences in the geometries of the foam pieces define the voids in the overall foam.
In another variation the voids are configured to form cooling air passages for cooling air circulated in the disk drive enclosure system. In this instance the voids can be in the form of channels in the foam, or openings through the foam, which form the cooling air passages. The voids can thus be selectively sized and located within the foam to not only tune the compliance of the foam to a desired level, but also to facilitate the flow of cooling air in the disk drive enclosure system. Since the disk drive enclosure system is configured to receive a plurality of disk drives, in this instance the voids can be located proximate to the locations where the disk drives will be mounted to the cage.
A further embodiment of the present invention provides for a method of increasing compliance of a foam component of a foam system used in a disk array system, the foam system configured to insulate disk drives in the disk array system from mechanical shock and vibration. The method includes providing a foam component of the foam system, and selectively forming a plurality of voids in the foam component. The voids are preferably selectively formed to thereby increase the compliance of the foam component (i.e., to cause an increase between the state where the voids are not yet formed in the foam component, and the state where the voids are formed in the foam component).
Typically, the foam component will be defined by a first compliance prior to forming the voids therein. Then, after the voids are formed in the foam component it will be defined by a second compliance, the second compliance being higher than the first compliance. That is, the voids can make the foam component more compliant, or subject to greater deformation under a constant load. The second compliance can be a predetermined compliance, and the voids can be formed in the foam component until the second compliance is achieved. That is, the compliance of the foam component can be xe2x80x9ctunedxe2x80x9d or adjusted by forming the voids until the desired compliance is achieved.
These and other aspects and embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein: